Effects of type of magnet attachment and implant angulation in two implant overdenture models

PURPOSE: The purpose of this study is to evaluate the effects of type of magnet attachment and implant angulation in two implant overdenture models.MATERIALS AND METHODS: Magnet attachments used in this study were flat and dome types (MGT5515, MGT5520D, Dentium Co., Seoul, Korea). Two implants with keepers were inserted in the resin blocks at a distance of 24 mm. For the first model, the implants were parallel to the vertical and perpendicular to the horizontal; for the second model, both were angulated 5 degrees to the mesial; for the third model, both were angulated 10 degrees toward the mesial. The retentive force was measured in both vertical and lateral directions. Statistical analyses were performed using SPSS software version 22.0 (α=.05).RESULTS: The flat type magnet attachment showed the highest lateral retentive force in the 20° divergent group (P<.05) and the dome type magnet attachment showed the highest lateral retentive force in the parallel group (P<.05). The vertical and lateral retentive force of the dome type magnet attachment was greater than that of the flat type magnet attachment in every direction (P<.05).CONCLUSION: Within the limitations of this study, the dome shape magnet attachment can resist vertical and lateral retentive force more superiorly than the flat type magnet attachment, regardless of angle, in the mandibular two implant model.

Effect of impression coping and implant angulation on the accuracy of implant impressions: an in vitro study

PURPOSE: The purpose of this study was to compare the accuracy of the implant master cast according to the type (pick-up, transfer) and the length (long, short) of the impression copings. MATERIALS AND METHODS: The metal master cast was fabricated with three internal connection type implant analogs (Osstem GS III analog), embedded parallel and with 10degrees of mesial angulation to the center analog. Four types of impression coping were prepared with different combinations of types (transfer, pick-up) and lengths (long, short) of the coping. The impressions were made using vinyl polysiloxane (one step, heavy + light body) with an individual tray, and 10 impressions were made for each group. Eventually, 40 experimental casts were produced. Then, the difference in the distance between the master cast and the experimental cast were measured, and the error rate was determined. The analysis of variance was performed using the SPSS (v 12.0) program (alpha = .05), and the statistical significance was set at P < .05. RESULTS: The ANOVA showed that the pick-up type impression coping exhibited a significantly lower error rate than the transfer type. However, no significant difference was observed with respect to the length of the impression coping. Additionally, no significant difference was observed between the parallel and mesial angulated groups. CONCLUSION: Within the limitations of this study, the pick-up type impression coping exhibited a more accurate implant master cast than the transfer type in parallel group. The accuracy of the implant master cast did not differ for different lengths of impression coping of at least 11 mm. Additionally, the accuracy of the implant cast was not different for the parallel and 10degrees mesial angulated groups.

3D finite element analysis of overdenture stability and stress distribution on mandibular implant-retained overdenture / 대한치과보철학회지

STATEMENT OF PROBLEM: Recently there are on an increasing trend of using implants -especially in edentulous mandible of severly alveolar bone recessed. PURPOSE: The aim of this study was to analyze the displacement and stress distribution of various mandibular implant-retained overdenture models supported by two implants in interforaminal region under the occlusion scheme load. MATERIAL AND METHOD: FEA models were made by the 3D scanning of the edentulous mandibular dentiform. The three models were named as Model M1, M2, and M3 according to the position of implants: M1, Lt. incisor area, M2, Canine area, and M3, 1st Premolar area. Inter-implant angulation model was named as M4. Conventional complete denture was named M5 and used as a control group. Ball implant and Gold matrice were used as a retentive anchors. The occlusion type loads were applied horizontally over each tooth. RESULTS: 1. In mandibular implant retained overdenture Canine Protected Occlusion type load resulted in higher levels of stress to the implants and female matrices than other types of loads. 2. The overdenture model, M1, with implants in lateral incisor areas resulted in lower stress concentration to the implants and female matrices than other models. 3. In mandibular implant retained overdenture the stresses of the implant and female matrice were lower in mesially inclined implant than these of parallel installed implant. CONCLUSION: Lateral incisor areas could be the best site for the implants in mandibular implant-retained overdenture. The mandibular implant retained overdenture models mentioned above showed to the lowest stress to the implants and female matrices.